Atrioventricular synchronized dual chamber pacing modes, such as the multi-programmable VDD, VDDR, DDD and DDDR pacing modes, have been widely adopted in implantable pacemakers for providing atrioventricular synchronized pacing. A pacemaker operating in such a pacing mode may include an atrial sense amplifier that detects atrial depolarizations and generates an atrial sense event signal in response to an atrial depolarization. In some pacemakers, the same electrode that senses atrial events can also deliver an atrial pacing pulse when the atrium fails to activate spontaneously.
Following the atrial event, whether sensed or paced, and following the expiration of an atrioventricular delay, the pacemaker supplies a ventricular pacing pulse to one or more ventricles. In some pacemakers, delivery of the ventricular pacing pulse is inhibited when the ventricles activate spontaneously. Some DDD and DDDR mode pacers employ separate atrioventricular delays for sensed and paced atrial events.
The atrioventricular delay is important to atrioventricular synchrony and hemodynamic performance. In general, atrioventricular synchronous pacemakers have the capability of tracking the patients natural sinus rhythm and preserving the hemodynamic contribution of the atrial contraction over a wide range of heart rates. The importance of atrioventricular mechanical synchrony is described in greater detail in commonly assigned U.S. Pat. No. 5,626,623, incorporated herein by reference in its entirety.
In prior art pacemakers, the atrioventricular delay need not be a fixed interval, but can be lengthened or shortened in response to various factors. Some prior art devices, for example, use pressure data obtained from the right and/or left ventricles of the heart to adjust the atrioventricular delay. In particular, prior art devices have adjusted the atrioventricular delay as a function of the estimated pulmonary artery diastolic (ePAD) pressure measured in the right ventricle, or as a function of heart contractility, or as a function of measured cardiac output. Other prior art devices have adjusted the atrioventricular delay and observed the resulting effects on ventricular pressures. Examples of these techniques and/or devices may be found in the issued U.S. Patents listed in Table 1 below.
TABLE 1U.S. Pat. No.InventorIssue Date5,024,222ThackerJun. 18, 19915,292,340Crosby et al.May 8, 19945,312,452SaloMay 17, 19945,334,222Salo et al.Aug. 2, 19945,368,040CarneyNov. 29, 19945,454,838Vallana et al.Oct. 3, 19955,466,245Spinelli et al.Nov. 14, 19955,487,752Salo et al.Jan. 30, 19965,535,752Halperin et al.Jul. 16, 19965,540,727Tockman et al.Jul. 30, 19965,584,868Salo et al.Dec. 17, 19965,626,623Kieval et al.May 6, 19975,643,327Dawson et al.Jul. 1, 19975,800,471BaumannSep. 1, 19985,810,735Halperin et al.Sep. 22, 19985,836,987Baumann et al.Nov. 17, 19986,144,880Ding et al.Nov. 7, 20006,280,389 B1Ding et al.Aug. 28, 2001All patents listed in Table 1 above are hereby incorporated by reference herein in their respective entireties. As those of ordinary skill in the art will appreciate readily upon reading the Summary of the Invention, Detailed Description of the Preferred Embodiments and claims set forth below, many of the devices and methods disclosed in the patents of Table 1 may be modified advantageously by using the techniques of the present invention.